As liquid dishwashing detergent formulations become increasingly popular with the consumer, the performance of such detergent compositions for cleaning kitchen utensils, such as glasses, dishes and other apparatus, becomes more important. Many performances characteristics are associated with this type of detergent formulation, among which are foamability, detergency, soil suspending ability, and mildness. In addition, the consumer has become concerned with both the final appearance of the objects that are washed and the ease with which washing, rinsing and the drying of the kitchen utensils can be accomplished.
Spotting may be referred to as resulting from the break-up of a once continuous liquid film followed by the isolation of liquid patches that become stranded on the solid surface. Upon the drying of these isolated liquid patches, spots will form from the solid residue that was dissolved or suspended in the liquid. One of the disadvantages associated with liquid dishwashing detergent compositions, therefore, is the need to dry the washed objects or apparatus with a towel so that spot and film formation from the minerals in the rinse water can be avoided or minimized to a large extent. Moreover, because of the amount of water that remains undrained on the glassware and plates and kitchen utensils, etc., the towel drying process tends to become time consuming and an additional burden to the consumer, thereby leaving it more desirable to let the washed utensils or apparatus drain and dry by themselves under ambient conditions.
Various attempts have been made to minimize the effect of the water hardness residue and film-forming deposits on washed kitchen utensils by applying various additives in the detergent formulations, either by complexing the water hardness salts, or by formulating special rinsing agents. However, the incorporation of complexing and/or soil suspending agents in the liquid formulations create processing and formulation problems, while any of the special rinsing agents that have been disclosed heretofore must be packed and applied separately in the washing solution.
One approach that has been utilized to reduce the need for towel drying and to increase the drainage of the washed kitchen utensils, has been to incorporate an agent into the formulation that can adsorb on the surface of the washed kitchen utensils to alter its wettability and surface properties, thereby modifying the drainage behavior of the rinsed water on the washed object. Under desirable conditions of wettability, the rinse water from the washed object will rapidly "sheet-off" the utensil, for example drinking glasses, thereby leaving the surface dry. This rapid "sheeting-off" effect reduces the effort involved in drying the washed objects and also improves their final appearance in terms of minimizing or altogether obviating the spotting and filming associated with suspended soil and water hardness.
Applicants have unexpectedly discovered that a liquid detergent composition containing a relatively small amount of polyvinylpyrrolidone or a copolymer of N-vinylpyrrolidone and dimethylamino-ethylmethacrylate, each having specific molecular weight limitations, and optionally, a small amount of an alkali metal salt of casein, e.g., sodium caseinate, when added to an anionic surfactant, nonionic surfactant, or mixtures thereof, provides an excellent washing and cleaning composition with much improved drainage properties so as to render the cleaned objects virtually free from spotting and/or filming.